Carburetor



April 21, 1953 D. STOLTMAN CARBURETOR Filed Sept. 23 1950 3 //v vs/vroeDONALD STOLTMAN HIS, 447' TUBA/5Y5 Patented Apr. 21,1953

UNITED STATES PATENT GFFICE poration of Delaware Application September23, 1950, Serial No. 186,419

8 Claims.

. 1 This invention relates to carburetors for internal combustionengines, particularly for automotive use and is an improvement on thetype of carburetor disclosed in the currently pending application SerialNo. 109,347, filed August 9,

The principal object of the present invention is to provide a fuelpassage for conveying fuel from the fuel chamber to the fuel inlet orinlets through which fuel is discharged into the mixture passage of thecarburetor which is so constructed that there will be a substantiallyeven flow of fuel through such passage under all operating conditionsand temperatures and in which the formation of vapor bubbles largeenough to materially obstruct the flow of fuel is prevented at anytemperature at which the engine may operate.

The above object is attained according to the present invention by theprovision of a fuel conduit comprising two parts, one of which is asubstantially vertical passage formed in a member extending downwardlyinto the fuel in a constant level fuel chamber, which connects at itsupper end with a substantially horizontal passage leading to the mainand idling fuel inlets. At the point Where the vertical and horizontalpassages join, there is formed a small chamber, the walls of which areflared outwardly along a horizontal axis through such chamber in thedirection of fuel flow therethrough. The walls of this chamber are alsoflared outwardly in a downward direction and its top surface is notnormal to the axis of the vertical fuel passage, but lies at an obtuseangle thereto with respect to the direction of fuel flow. The chamberthus formed is without any sharp corners and while the provision of thischamber does not prevent completely the formation of vapor bubbles, itsubstantially prevents the collection and building up therein of bubblesof sumcient size to materially interfere with the even flow of fuel.This function is of very considerable importance particularly duringidling at relatively high temperatures. Any bubbles which are formed areof small size andpass on to the fuel inlets without causing appreciableirregularity of flow of the latter. A chamber suchas described is shownand claimed in the application of Olsen, 5. N. 132,821, filed December14, 1949. Associated with the chamber in the device shown in suchapplication is a substantially horizontal passage which leads from saidchamber and through which fuel flows to the fuel inlets, said passagebeing divided into two parts by ahorizontal partition plate and intheOlson device almost all of such vapor bubbles as are formed 2 passthrough the upper part of the horizonta passage.

According to the present invention, instead of having a flat horizontalpartition plate in the fuel delivery conduit which leads from theaforementioned chamber as in the Olson device, applicant has provided apartition in the fuel conduit which is twisted or spiral in form and isso arranged that at the inlet end of the fuel passage adjacent thechamber, the plate is horizontal, but at the opposite or discharge endof the passage the plate is vertical, so that the passage on each sideof the partition plate, at the discharge end of such passage, is at thesame level.

When a flat horizontal partition is used and the discharge from the twoparts of the delivery passage is at different levels, under someconditions, for example, when the carburetor is tilted or at an angle,the flow through the upper part of I the delivery passage, above thepartition plate, is

apparently retarded to some extent which reduces the effectiveness ofthe partition. When a spiral or twisted partition of the form shownherein is employed. this retarding effect on the flow on one side of thepartition, under the circumstances remation of a homogeneous fuelmixture, particularly at relatively high velocities.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Fig. l is a vertical section through the carburotor and fuel supplypassage.

Fig. 2 is a detail section showing the construction of the fuel conduitwhere the vertical and horizontal passages connect.

Fig. 3 is a horizontal section on the line 3-3 of Fig. 2.

Figs. 4, 5 and 6 are sections on the lines 4--4, ti -5 and Etrespectively, of Fig. 3.

Referring to Fig. 1, the carburetor shown there in comprises threeseparate castings numbered I, 2 and 3, respectively. The casting l isthe carburetor outlet which is adapted to be connected with the intakemanifold in the usual manner, the casting 2 is positioned above theoutlet casting l and has a constant level fuel chamber 2a formedtherein, while the casting 3 forms a cover for the fuel chamber and alsohas the air intake 4 formed therein. These three castings are separatedby gaskets to form tight joints and to limit the transfer of heatbetween the castings as much as possible by preventing any metalliccontact of the castings with each other.

In the outlet casting l, a throttle shaft 5 is suitably journalled andsecured to such shaft is the usual throttle valve 6 which is manuallyadjustable by means not shown to control the volume of combustiblemixture which is supplied by the carburetor to the engine.

In the casting 3 a choke valve 7 is positioned and this valve is securedto a shaft 8 Which is suitably mounted in the casting 3 for rotation.The choke valve in the carburetor disclosed herein is manually operatedand, when the engine is operating at normal temperature, is adapted tobe positioned in wide open position so as not to restrict the quantityof air entering the carburetor, but is adapted to be closed, or partlyclosed, by the manual operating connections when the engine is startedcold in order to facilitate starting, the position to which the chokevalve is moved being dependent upon the temperature at the time ofstarting. The choke valve is adapted to be moved to different positionsby means of the arm numbered 9 which is adapted to be operated by aconnection leading to the dash which is not shown herein, but is aconventional con struction. The arm 9 operates the choke valve throughmechanism which need not be described herein, but is fully shown anddescribed in the copending application above referred to. It may besaid, however, that the operation of the choke valve by the arm 9 iseffected through a spring Ill which holds the choke valve yieldinglyclosed, so that when the engine starts to run under its own power, theincrease in engine suction which then occurs can pull the valve open tosome extent against the force of the spring 10, so as to preventover-choking.

In the carburetor shown herein, the choke valve is also designed tooperate the throttle so as to move the throttle slightly toward openposition when the choke valve is moved to its fully closed position inorder that the idling speed may be somewhat increased when the chokevalve is closed. This is done for the purpose of providing a somewhatfaster than normal idling when the choke valve is closed at lowtemperatures which is desirable to prevent stalling. The operatingconnections between the choke valve and the throttle valve for effectingthis movement are indicated generally by the reference numeral ll. Sincethis mechanism has nothing to do with the invention in this application,it is not illustrated in detail and will not be described, but suchmechanism is'fully shown and described in the aforesaid copendingapplication.

As already indicated, air is admitted to the carburetor through the airinlet 4 and fuel is supplied to thecarburetor through a main fuel nozzlel2 which terminates at the throat of a small Venturi tube 13 which,itself, terminates at the throat of a large Venturi tube I l integralwith the casting 2 and forming a part of the mixture passage whichextends vertically through the carburetor. The purpose of these Venturitubes is, of course, to increase the velocity of air flow past the endof the main fuel nozzle E2 to create a partial vacuum adjacent thenozzle outlet in the usual and well known manner. Fuel is also suppliedto the intake passage by an idling fuel inlet which is not shown herein,but which termi= 4 nates in an orifice communicating with the intakepassage at the point adjacent and slightly pos terior to the edge of thethrottle valve 6 when the latter is in closed position.

Fuel is supplied to both of these fuel inlets from the fuel chamber 2aand fuel is supplied to the latter through a coupling i5 which isscrewed into the casting 3 and to which a fuel supply pipe extending tothe main fuel tank of the vehicle is adapted to be connected. Fuel whichis supplied through the coupling l5 enters a passage l6 formed in thecasting 3 and flows through a passage in a nipple ll, which is screwedin the wall of the casting 3, and communicates with the fuel bowl 2awhen the parts are assembled as shown in Fig. l. The flow of fuelthrough the passage I! into the bowl is controlled by a valve I 8 whichcooperates with the passage 17 and rests on one arm of a lever l9 whichis pivoted on a pin 28 fixed in position in the wall of the fuel chamber2a. The lever I9 is connected to the floatmechanismwhich is not shown,but which is received within'the chamber 2a and when the fuel'level insaid chamber reaches a definite height, the float lifts the lever 59 soas to close the valve I8 and cut off the flow of fuel into the floatchamber in the usual way. The float mechanism is of conventionalconstruction and has nothing to do with the invention which is claimedin this application.

Before describing the fuel passage which conveys fuel from the floatchamber 2a to the main and idling fuel inlets, the construction of whichconstitutes the subject matter to which the claims of this applicationare directed, attention is called to the fact that the carburetor isprovided with an accelerator pump which is operated manually upon suddenopening movements of the throttle to provide a charge of fuel inaddition to the fuel supplied by the ordinary fuel inlet, in order toenrich the mixture for acceleration in the usual way. The constructionof this accelerator pump constitutes no part of the present invention,but the pump includes a cylinder 25 into which fuel flows from the floatchamber 20:, through a passage, not shown, and slidable in the cylinderis a pump piston 26 which isoperated by a spring 21 that is compressedwhen the throttle is opened suddenly, by means of an arm 26a which ispulled downwardly when the throttle is opened. This compression of thespringeffects a delayed downward movement of the piston 26 which takesplace as the spring expands following its compression by the throttle,as the latter is opened and as the piston moves downwardly, in themanner de scribed, it forces fuel from the space below the piston intothe mixture passage to supply the additional fuel above referred to foracceleration purposes. This pump mechanism is fully shown and describedin the copending application above referred to and will not be furtherdescribed herein, since its construction is entirely immaterial so faras the present invention is concerned. A tube 28 which connects theupper end of the cylinder 25 with the carburetor intake serves as a ventfor escape of any fuel bubbles which may collect within the cylinder 25and as a vent for the fuel chamber 2a. 7

The construction which has been generally described above is the same asthat disclosed in application S. N. 109,347 and'the construction of theentire carburetor is the same as what is shown in such applicationexcept the fuel conduit which supplies fuel to the main and idle fuelinlets. In this application, as in the earlier application, such fuelconduit comprises three parts or passages which together make up aconduit shaped substantially like an inverted U, one part or passagebeing substantially vertical and extending downwardly into the floatchamber and connecting at its upper end with a horizontal passageformed. in casting 3, which, in turn, connects at its other end with asubstantially vertical. passage that extends downwardly to the idlingfuel inlet, the main fuelinlet communicating with the horizontal portionof the passage substantially midway between its ends. As-shown in Fig.-1, the fuel conduit includes a vertical pas sage formed in a member 3|which, at its upper end, is secured in any suitable way in a bore orchamber 3m formed in the casting 3. This member, at its lower end, has acalibrated plug 32 screwed into it which meters the fuel sup"- plied topassage 30. Communicating with the chamber 3la is a horizontal passage33- which, at its left end, as shown in Fig. l, connects with a verticalpassage 34- which extends downwardly in the wall of the casting 2 andcommunicates at its lower end with a passage 35 which leads to theidling fuel inlet, which is not shown herein but is of the sameconstruction as shown in the earlier application. As shown, the chamber31a is of larger diameter than either of the passages 30 or 33, but doesnot have to be of the exact size shown. The horizontal portion 33 ofthefuel conduit is of different diameters, that part of the passagelying between the chamber 3|a and the point of connection with the mainnozzle being smaller than that part 35 of the passage 33 which lie tothe left of the main nozzle in Fig. l. A plug 3! closes the left end ofthe passage and a tube 38 is fitted in that part of the fuel passagenumbered 35. Such tube has a restricted opening 38a at its right end andterminates somewhat to the right of the vertical passage 34. A pluralityof orifices 39 are provided immediately above the main nozzle l2 toadmit air for purposes of effecting atomization of the fuel and abushing 40 having a small orifice 4i therein is positioned within themain nozzle l2 to cause a flow therethrough at high velocity and to aidin the atomization of the fuel. This fuel passage as so far described,is of the same construction as that shown in the earlier application,except that the chamber am is not disclosed therein. In such applicationa passage such as 30 merely connects with another passage such as 33 ofthe same size as the passage 39, the axis of which is normal to thepassage 38.

In the earlier application the passages corre-' sponding to 30 and 33were simple cylindrical bores. and formed a sharp corner at the pointwhere they connected. It was found that there was some tendency,particularly at high temperatures, for vapor bubbles to form and collectin this corner and for such vapor bubbles to gradually grow in sizeuntila bubble of such large size was formed that the flow of fuelthrough the passage was partly or wholly restricted, particularly duringidling. This bubble would increase in size until the passage was nearlyblocked and would then break loose and pass through the passage 33 andfinally out into the carburetor. This results in a somewhat intermittentand irregular iiow of fuel, causing some degree of irregularity ofoperation during idling. The device which constitutes the invention towhich this application is directed is designed primarily to prevent anyblocking of the fuel supply passage and any irregularity of engineoperation: resulting therefrom at any operating. temperature. Therefore, instead of having a simple fuel conduit such as shown in theearlier application and described above, according to the presentinvention, the chamber 31a is provided at the point of connection of thepassages 30 and 33. As already stated, the walls of this chamber aretapered or flared, so as to present no sharp corner in which vaporbubbles would tendto collect and build up as previously described, andwhile small bubbles are formed when operating at relatively hightemperatures, these are not large enough to obstruct the flow and simplymove along through the con-'- duit with the liquid fuel to the fuelinlets and into the mixture passage.

As illustrated, the chamber am has an upper surface 65 which is inclinedupwardly in the direction of fuel. flow, asindicated in Figs. 1 and 3,and has side walls 46 and 41 which are flared outwardly in a downwarddirection from the top surface 45 and terminate in the cylindricalopening 48 in which the upper end of the member 3| is received. Theshape of the surfaces 46, 41 and 48 will be readily understood fromFigs. 2, 5 and 6. As best shown in Fig. 2, the surfaces 46 and 41 arealso flared outwardly in the direction of fuel flow along the axis ofthe horizontal passage 33.

Obviously, the top and sides of the chamber 31a merge into a singlesmooth surface free from any sharp corners and progressively enlargingin the direction of fuel flow.

The chamber 3la which has been previously described, has been found togreatly reduce the tendency for vapor bubbles to collect and build up toa size sufficient to materially interfere with the fuel flow becausethere are no sharp corners which might hold a bubble during the buildingup process; According to the present invention, however, means have beenprovided which will break up any bubbles which might be formed in suchchamber into smaller size and will cause such small bubbles to flowthrough the passage leading from the chamber to the fuel inlets at highvelocity so as to produce a substantially constant and regular flow offuel during idling as well as when the main fuel inlet is functioningand the engine is operating under load.

This means comprises a partition plate 49 which is positioned in thehorizontal passage 33 and divides this passage into two parts, 533 and5t. This partition is twisted so as to give a whirl- I i ng motion tothe fuel flowing through the passages as and El. As shown, the plate 59is twisted through an angle of degrees, lying in a horizontal plane atits right end and in a vertical plane at the left end. However, theinvention is not limited to a plate, such as 49, of any particular formand the twisting of the plate can be more or less as desired as long asthe passage 33- at its intake end is divided horizontally and at itsdischarge end is divided vertically. It has also been found that thepartition plate gives better results when it is somewhat shorter thanthe passage 33 and excellent results are obtained if its length is aboutfour-fifths, or a little more than that of passage 33 from the end ofpassage 39 to the main fuel inlet.

The use of a flat partition plate 9, such as shown in application S. N.132,821, has the effect of causing any small bubbles which may be formedin the chamber 31a. to flow primarily through the space 5!} above thepartition and at considerably higher velocity than the substantiallysolid fuel column which flows through space 5 I. As already stated,under some operating conditions, particularly when the carburetor istilted during idling at high temperatures, so that the discharge end ofpassage 33ris substantially lower than the intakeend of suchpassage,.the velocity of flow through the space v50 is materiallyreduced and this correspondingly reducesthe effectiveness of thepartition plate and interferes with the supply of fuel for idling,tending to produce irregular operation of the engine at idling. Byprovision of the spiral partition plate, in accordance with the presentinvention, this reduction in flow velocity through the space 50 islargely avoided and smoother idling operation is secured. Also bycausing the liquid fuel and fuel. vapor to move through spiral pathsformed by passages Eiiand which discharge such fuel and vapor into thespace to which air is introduced through orifices 35, the mixing actionis aided particularly at relatively high flow velocities.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows: H

. l. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the-flow of combustiblemixture therethrough, air and fuel inlets for admitting air and fuel tosaid mixture passage, a fuel conduit for conveyingfuel from the fuelchamber to themixture passage, said fuel conduit comprising a fuelpassage communicating at one end with the fuel chamber and a second fuelpassage communicating at one end with the discharge end of the firstfuel passage and conveying fuel therefrom toward the mixture passage,the wall surface of said conduit at the point of connection of saidfirst and second passages being formed in such a way that no sharpcorners are presented by said wall surface whereby the formation andretention of vapor bubbles in said conduit at the point of connection ofsaid passages is substantially prevented and a partition plate in saidsecond fuel passage dividing said passage into two separate conduitsthrough which the fuel flows, said plate being horizontal adjacent theinlet end of the passage so as to divide the passage into upper andlower conduits and vertical adjacent the discharge end of the passage soas to divide such passage into two conduits on the same horizontalplane.

2. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the flow of combustiblemixture therethrough, air and fuel inlets for admitting air and fuel tosaid mixture passage, a fuel conduit for conveying fuel from the fuelchamber to the mixture passage, said fuel conduit comprising a fuelpassage communicating at one end with the fuel chamber and a second fuelpassage communicating at one end with the discharge end of the firstfuel passage and conveying fuel therefrom toward the mixture passage,the wall surface of said conduit at the point of connection of saidfirst and second passages being formed in such a way that no sharpcorners are presented by said wall surface whereby the formation andretention of vapor bubbles in said conduit at the point of connection ofsaid passages is substantially prevented and a partition plate in saidsecond fuel passage dividing the passage into two separate fuel conduitsthrough which fuel flows, said plate I the inlet end of said second'fuelpassage and being twisted substantially ninety degrees so that it liesin a substantially vertical plane adjacent the outlet end of said secondfuel passage.

3. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the flow of combustiblemixture therethrough, air and fuel inlets for admitting air and fuel tosaid mixture passage, a fuel conduit for conveying fuel from the .fuelchamber to the mixture passage, said fuelconduit comprising a fuelpassage communicating at one end with the fuel chamber and a second fuelpassage communicating at one end with the discharge end of the firstfuel passage and conveying fuel therefrom toward the mixture passage,the wall surface of said conduit at the point of connection of saidfirst and second passages being formed in such a way that no sharpcorners are presented by said wall surface whereby the formation andretention of vapor bubbles in said conduit at the point of connection ofsaid passages is substantially prevented and a partition plate in saidsecond fuel passage dividing the passage into two separate fuel conduitsthrough which fuel flows and of a length slightly less than that of thesecond fuel passage, said plate lying in a substantially horizontalplane adjacent the inlet end of said second fuel passage and beingtwisted substantially ninety degrees so that it lies in a substantiallyvertical plane adjacentthe outlet end of said second fuel passage.

4. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the flow of combustiblemixture therethrough, air and fuel inlets for admitting air and fuel tosaid mixture passage, a fuel conduit for conveying fuel from saidconstant level fuel chamber to the mixture passage, and comprising anupwardly extending passage which communicates at its lower end with thefuel chamber, a second passage extending substantially horizontally andforming a chamber at its point of connection with the upwardly extendingpassage having side walls which are flared outwardly in a downwarddirection and horizontally in the direction of flow of fueltherethrough, and a top surface tapered upwardly in the direction offlow of fuel therethrough, whereby the flow of fuel is facilitated andthe retention of vapor bubbles therein of sufficient size to interferewith the fuel fiow is prevented, a partition plate in said second fuelpassage, said plate lying in a substantially horizontal plane adjacentsaid chamber so as to divide the fuel passage into upper and lowerconduits and in a substantially vertical plane adjacent the dischargeend of the passage so as to form two separate fuel conduits at the samelevel.

5. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttlevalve for'controlling the flow of combustiblemixture therethrough, air and fuel inlet's for admitting air and fuel tosaid mixture passage, a fuel conduit for conveying fuel from saidconstant level fuel chamber to the mixture passage'and comprising agenerally vertical passage formed in a member extending downwardly intothe'fuel in said fuel chamber and entirely surrounded by the fueltherein in order to prevent the heating of said member by conductivityand to reduce the formation of vapor bubbles in acease said passage, asubstantially horizontal passage connecting with the vertical passage atits upper end and forming a chamber at its point of connection with thevertical passage having tapered side and top walls, whereby theretention in said chamber of any vapor bubbles that may be formed isprevented and the flow of fuel therethrough is facilitated, a partitionplate in said second fuel passage of a length slightly less than thepassage, said plate lying in a substantially horizontal plane adjacentsaid chamber so as to divide the fuel passage into upper and lowerconduits and in a substantially vertical plane adjacent the dischargeend of the passage so as to form two separate fuel conduits at the samelevel.

6. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the flow of combustiblemixture therethrough, air and fuel ina lets for admitting air and fuelto said mixture passage, a fuel conduit for conveying fuel from saidconstant level fuel chamber to the mixture passage, and comprising anupwardly extending passage which communicates at its lower end with thefuel chamber to receive fuel therefrom, a second passage extendingsubstantially horizontally and connecting at one end with the upwardlyextending passage, a partition plate in said second fuel passage, saidplate lying in a substantially horizontal plane adjacent the inlet endof the fuel passage so as to divide the passage into upper and lowerconduits and in a substantially vertical plane adjacent the dischargeend of the passage so as to form two fuel conduits at the same level.

7. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the now of combustiblemixture therethrough, air anclfuel inlets for admitting air and fuel tosaid mixture passage, a fuel conduit for conveying fuel from saidconstant level fuel chamber to the mixture passage and comprising anupwardly extending passage which communicates at its lower end with thefuel chamber to receive fuel therefrom, a second passage extendingsubstantially horizontally and connecting at one end with the upwardlyextending passage, a partition plate in said second fuel passage of alength slightly less than the passage, said plate lying in asubstantially horizontal plane adjacent the inlet end of the fuelpassage so as to divide the passage into upper and lower conduits and ina substantially vertical plane adjacent the discharge end of the passageso as to form two fuel conduits at the same level.

8. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the flow of combustiblemixture therethrough, air and fuel inlets for admitting air and fuel tosaid mixture passage, a fuel conduit for conveying fuel from the fuelchamber to the mixture passage, said fuel conduit comprising a fuelpassage communicating at one end with the fuel chamber and a second fuelpassage communicating at one end with the discharge end of the firstfuel passage and conveying fuel therefrom toward the mixture passage,the wall surface of said conduit at the point of connection of saidfirst and second passages being formed in such a way that no sharpcorners are presented by said wall surface whereby the formation andretention of vapor bubbles in said conduit at the point of connection ofsaid passages is substantially prevented and a spiral partition plate insaid second fuel passage to cause the fuel flowing therethrough to movein a spiral path, the partition plate being so positioned in said fuelpassage that its end adjacent the point of junction of the two fuelpassages lies in a substantially horizontal plane when the carburetor isattached to the engine and the opposite end of said plate lies in asubstantially vertical plane.

DONALD STOLTMAN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,777,141 Howden Sept. 30, 1930 1,893,920 Winfield Jan. 10,1933 2,012,665 Gustafsson Aug. 27, 1935 2,126,132 Paasche Aug. 9, 1938

